The BGS Lexicon of Named Rock Units — Result Details

Borrowdale Sill Suite

Computer Code: BVGS Preferred Map Code: notEntered
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Aphyric and porphyritic basalt, basaltic andesite, andesite, dacite and rhyolite, many with peperitic breccia margins.
Definition of Lower Boundary: Sills within, and contemporaneous with the Borrowdale Volcanic Group, the lower boundary of which is defined at the contact of each sill. Most occur within the Borrodale Volcanic Group, though some are present in the Skiddaw Group and were previously interpreted as lava.
Definition of Upper Boundary: Defined by the contact of each sill.
Thickness: Individual sills up to 400m thick, typically much less.
Geographical Limits: Within the outcrop areas of the Borrowdale Volcanic Group and Skiddaw Group, Cumbria.
Parent Unit: Caledonian Supersuite (CIGSS)
Previous Name(s): Sills in the Borrowdale Volcanic Group [Obsolete Name and Code: Use BVGS] (-2033)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Pets Quarry, Kirkstone. Branney and Suthren, 1988. 
Reference(s):
Millward, D, Johnson, E W, Beddoe-Stephens, B, Young, B, Kneller, B C, Lee, M K, Fortey, N J, Allen, P M, Branney, M J, Cooper, D C, Hirons, S, Kokelaar, B P, Marks, R J, McConnell, B J, Merritt, J W, Molyneux, S G, Petterson, M G, Roberts, B, Rundle, C C, Rushton, A W A, Scott, R W, Soper, N J, and Stone, P. 2000. Geology of the Ambleside district. Memoir of the British Geological Survey, England and Wales, Sheet 38. 
Millward, D. 2002. Early Palaeozoic magmatism in the English Lake District. Proceedings of the Yorkshire Geological Society, Vol. 54, Part 2, 65-93. 
Branney, M J, and Suthren, R J. 1988. High level peperitic sills in the English Lake District: distinction from block lavas and implications for the Borrowdale Volcanic Group stratigraphy. Geological Journal, Vol. 23, 171-187. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E029 E048 E038 E037 E030 E039